Ecotypic variation among switchgrass populations from the northern USA

Switchgrass (Panicum virgatum L.) is a widely adapted warm-season perennial that has considerable potential as a biofuel crop. Broad species adaptation, natural selection, and photoperiodism have combined to create considerable ecotypic differentiation in switchgrass. The objective of this study was to characterize phenotypic variability among switchgrass ecotypes collected from prairie remnants in the northern USA. Thirty-eight switchgrass collections from 33 prairie-remnant sites and 11 switchgrass cultivars were evaluated for 2 yr at two locations (Arlington and Marshfield, WI) for nine variables: biomass yield, survival, dry matter, lodging, maturity, plant height, holocellullose, lignin, and ash. Autocorrelations, measuring spatial variation, and correlations between phenotypic distances and geographic distances were all nonsignificant. A small amount of variation for maturity, lodging, holocellulose, lignin, and ash could be attributed to latitude and/or longitude of the collection site. Populations from several of the westernmost collection sites clustered with cultivars from the Great Plains, suggesting an ecological basis for some of the phenotypic variation observed. However, there was a considerable amount of phenotypic variability between populations from collection sites in close proximity to each other. Hardiness zones (defined largely by temperature extremes) and ecoregions (defined largely by soil type and historic vegetation) partly define the phenotypic characteristics for many switchgrass populations collected from prairie remnants. Most switchgrass populations can be utilized for conservation and restoration projects throughout a combined ecoregion and hardiness zone without undue concern over contaminating, diluting, or swamping the local switchgrass gene pool.